144 DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XIII.) 



ducteous body can effect the discharge of the same kind of force, is curious, and, in 

 the case of elongated or irregularly shaped conductors, such as filaments or particles 

 of dust, the effect will often be very ready, and the consequent attraction very imme- 

 diate. 



1568. The effect described is also probably influential in causing those variations 

 in spark discharge referred to in the last series (1386. 1390.) : for if a particle of dust 

 were drawn towards the axis of induction between the balls, it would tend, whilst at 

 some distance from that axis, to commence discharge at itself, in the manner de- 

 scribed (1566.), and that commencement might so far facilitate the act (1417. 1420.) 

 as to make the complete discharge, as spark, pass through the particle, though it 

 might not be the shortest course from ball to ball. So also, with equal balls at equal 

 distances, as in the experiments of comparison already described (1493. 1506.), a 

 particle being between one pair of balls would cause discharge there in preference ; 

 or even if a particle were between each, difference of size or shape would give one 

 for the time a predominance over the other. 



1569. The power of particles of dust to carry off electricity in cases of high tension 

 is well known, and I have already mentioned some instances of the kind in the use 

 of the inductive apparatus (1201 .). The general operation is very well shown by large 

 light objects, as the toy called the electrical spider ; or, if smaller ones are wanted 

 for philosophical investigation, by the smoke of a glowing green wax taper, which, 

 presenting a successive stream of such particles, makes their course visible. 



1570. On using oil of turpentine as the dielectric, the action and course of small 

 conducting carrying particles in it can be well observed. A few short pieces of 

 thread will supply the place of carriers, and their progressive action is exceedingly 

 interesting. 



1571. A very striking effect was produced on oil of turpentine, which, whether it 

 was due to the carrying power of the particles in it, or to any other action of them, is 

 perhaps as yet doubtful. A portion of that fluid in a glass vessel had a large unin- 

 sulated silver dish at the bottom, and an electrified metal rod with a round termina- 

 tion dipping into it at the top. The insulation was very good, and the attraction and 

 other phenomena striking. The rod end, with a drop of gum water attached to it, 

 was then electrified in the fluid ; the gum water soon spun off in fine threads, and 

 was quickly dissipated through the oil of turpentine. By the time that four drops 

 had in this way been commingled with a pint of the dielectric, the latter had lost by 

 far the greatest portion of its insulating power ; no sparks could be obtained in the 

 fluid ; and all the phenomena dependent upon insulation had sunk to a low degree. 

 The fluid was very slightly turbid. Upon being filtered through paper only, it re- 

 sumed its first clearness, and now insulated as well as before. The water, therefore, 

 was merely diffused through the oil of turpentine, not combined with or dissolved in 

 it: but whether the minute particles acted as carriers, or whether they were not 

 rather gathered together in the line of highest inductive tension (1350.), and there. 



